Recall, the formula for determining the perimeter of a rectangle is expressed as
Perimeter = 2(length + width)
Given that
Perimeter = 4x + 10
length = x + 5,
it means that
4x + 10 = 2(x + 5 + width)
By opening the parentheses on the right, we would multiply each term inside it by the term outside. we have
4x + 10 = 2x + 10 + 2width
4x - 2x + 10 - 10 = 2width
2width = 2x
width = 2x/2 = x
Recall, the formula for finding area is expressed as
Area = length * width
Thus,
Area = (x + 5)x
By opening the parentheses, we would multiply each term inside it by the term outside. Thus,
Area = x^2 + 5x